As described in the above-referenced '370 application, legacy (copper) wirelines, which have historically served as a principal information transport backbone for a variety of telecommunication networks, have recently given way to or have been augmented by other signal transport technologies, particularly those capable of relatively wideband service. These include coaxial cable, fiber optic and wireless (e.g., radio) systems, the latter being especially flexible in that they are not limited to serving only customers having access to existing or readily installable cable plants.
In addition, there are many environments, such as, but not limited to portable data terminal equipments (DTEs), where a digital wireless subsystem may be the only practical means of communication. In order to provide digital communication service, the wireless (radio) subsystem must not only be interfaced with an existing digital network's infrastructure, which typically includes legacy wireline links coupled to an incumbent local exchange carrier (ILEC), such as a Bell operating company (RBOC) site, but the digital radio site which provides access to the wireline must also provide a source of electrical power. In many environments, the required power supply is either not readily available, or its cost of installation is prohibitively expensive.
In accordance with the invention disclosed in the '370 application, the lack of, or unacceptably high cost of installing a power supply for a wireless communication equipment, that is intended to wirelessly connect existing digital communication network equipment with a remote site, is successfully remedied by a span or loop-powered digital T1 radio, which is installable at a location (such as a rooftop or pole site) that does not readily afford access to a dedicated power supply for the radio.
For this purpose, as diagrammatically illustrated in FIG. 1, the loop-powered radio of the invention disclosed in the '370 application includes a line interface circuit 10 that is coupled to tip (T) and ring (R) wirelines of respective transmit and receive segments 21 and 22 of a powered T1 wireline link 20, to which T1 communication equipment, such as an indoor carrier service unit (CSU) 30, is coupled. The line interface circuit 10 contains coupling transformer circuitry that extracts (+/−48 V) DC voltages of the powered tip and ring wireline pairs for application to a DC-DC voltage converter power supply 40, and also interfaces digital payload data transported by the powered T1 link to a T1 framer chip 50. The DC-DC converter scales down the +/−48 VDC voltages supplied by the span to voltages (e.g., +5 V and +12 V) used to power the digital signaling and transceiver electronics of the radio.
The transceiver section 55 of the radio is preferably of standard (e.g. ‘blue tooth’-compatible) design and includes a transmitter unit 60, that is coupled to receive the digital baseband signals from T1framer chip 50 and perform modulation and up-conversion to an FCC-conformal band RF signal (e.g., 2.4 GHz or 5.8 GHz spread spectrum signal). The radio's receiver unit 70 performs down-conversion and demodulation of the RF signal to baseband for application of the 1.536 Kbps payload data to the T1 framer chip 50. By extracting electrical power from the line 20 and converting the extracted power to voltages for operating its transceiver and signal processing components, the invention disclosed in the '370 application effectively eliminates having to locate the radio where a separate dedicated power supply is either available or can be readily installed.
Now although the loop-power extraction functionality of the radio of the '370 application makes it possible to place the radio in a variety of not readily accessible locations, it also means that once so installed, the radio does not readily lend itself to changing and/or monitoring its configuration and operational parameters.